Naphtha or Rock Oil, is a yellow or brownish bituminous fluid, of strong penetrating odour, greasy to the touch, and so light as to float on alcohol. By exposure to the air it thickens into the substance called petroleum. There are copious springs of naphtha at Baku, on the shore of the Caspian Sea. There are also at Pitchford, in Shropshire, extensive beds of sandstone, saturated with this fluid, which is separated from the stone by distillation, and is sold under the name of Betton's British oil. The Russians and Persians use naphtha internally, as a cordial. Naphtha burns with a brilliant white flame, and is therefore much used in lamps, both at home and abroad.